No one who plays F3 should EVER have a cash flow issue provided you buy all the houses and shops as you play through the story line and do the sidequests. As long as you don't "rush" the story, you shouldl EASILY have 8M gold by the time you are king.. even if everything is set to LOW. If you want to push the storyline faster, you can set rents to normal. I don't advise anything above normal or people start to actually hate you (unless you don't care). Earning money in F3 is quite easy. All you need is an initial 20K from jobs (or sale of treasure) early on in the game, and you are good to go.
Here is a "trick" when you start a new game to start out "rich"
1) Before you start a new game....
2) turn on controller 2
3) sign in with a 2nd local profile (it does NOT have to be a live profile)
4) join it to your game
5) gift 100K-1M gold to the 2nd, local player, plus any weapons, clothes, etc
6) have the 2nd "player" save their game and exit
7) save your game and load your new game
8) have controller 2 join in
9) have player 2 gift your new player whatever you gave them
yes this works even when you are just starting out in the castle... you won't actually be able to get the gifts until you have proper access to the sanctuary.
This is also a VERY safe way to move items between local saves w/o having a live player steal them from you.